C language The first C language program and development tools

1. Selection of development tools
2. Tools you can use to write code: Notepad, UltraEdit, Vim,Xcode , etc.
3. Reasons to choose Xcode: Apple's official development tool, simplified development process, highlighted features
4. Use Xcode to create a new source code file for a C program (extension. C or. c)

• Open Xcode

• New file

• Select the type of file

• Enter a file name and a directory to select files for

• New Complete

• Delete all automatically generated content from the file, starting from zero

1. Code writing

1. Program Structure
   1. The structure of the C program: consists of functions

• Any C language program is composed of one or more program segments (small programs), each of which has its own function, which we generally call "functions". So, you can say that the C language program is made up of functions

1. Basic concepts of functions

• Function name: an infinite number of functions in a program, each with its own name
• Call (Execute) function: According to the function name can call the corresponding function, perform the corresponding function

1. The entrance to the C program

• The entrance to the C program is a function called main , referred to as the main function
• Regardless of the number of functions in the program, the main function is executed first

1. Writing Programs
   1. Write the main function (the contents of the curly braces {} are the body of the function)

int Main ()

{

return 0;

}

1. write multiple functions , and make calls

int Test ()

{

return 0;

}

int Main ()

{

Test ();

return 0;

}

1. Use the printf function to output content to the screen

#include <stdio.h>

int Main ()

{

printf ("Hello world!" );

return 0;

}

1. Compile
2. What is compiling: Translating C source programs into 0 and 1 that the computer can recognize
3. What compiler to use: Xcode3 using GCC,XCODE4 with LLVM compiler (front end with clang)
4. How do I compile a program using the Clang compiler?

• In the terminal, enter: Cc–c file name. C
• The compilation succeeds and the. O target file is generated

1. Compiler Error and warning features

• If the code has a syntax problem, the compiler will direct an error. and indicate the number of errors and the exact line number.
• As long as there are 1 errors, the program will not compile successfully and will not generate an. o file
• Warning messages are just some of the compiler's recommendations and do not affect compilation through

1. Link
2. What the link does: combine the. o file and the C-language function library to generate the executable file
3. done by the linker, the Clang compiler already contains the link directive

• In the terminal, enter: CC file name. O
• Link succeeds, generates a.out executable file

1. Run
2. Two modes of operation

• Directly double-click Open a.out File
• Use the./a.out directive in the terminal

1. After modifying the contents of the file, be sure to recompile, link, and then run
2. \ n Function: Carriage return to newline

1. Other clang instructions

• Modify executable file name: CC xxx.o-o filename
• Compile together, Link: cc xxx.c

1. Common Mistakes for beginners

• Do not write semicolons, use a Chinese semicolon
• string with double quotation marks, or single quotes, double quotation marks inside.
• The code is not written inside the main function, before the return
• File extension is not. C or. c, e.g.. txt
• Compile the file with absolute path, note where the target file is generated

1. Summarize
2. The process of running the whole program

1. Summarize the extension of common Files

• . c is a C language source file that is created when you write code
• . O is the target file that is generated when the compilation is successful
• . Out is an executable file that is generated when the link succeeds

1. Summary clang directive

• Compilation: Cc–c xxx.c
• Link: cc XXX.O
• Compile, Link: cc xxx.c
• Run the executable file:./a.out

1. What errors are encountered in development? How to solve?

• Syntax error, can be resolved by compiler errors
• Logic error, need to be patient to debug program

1. Learning Advice

• Learning to program is not learning English
• Readability of the program
• Beginners should not be too root to ask the bottom

1. Exercises

Output the following pattern in 2 different code types

************

* * Itcast * *

************

Content Source: Preach intelligence podcast Li Mingjie teacher Content

C language The first C language program and development tools